Tension control system



Dec. 3, 1940. w. G. cooK TENSION CONTRO-L SYSTEM 3 Sheets-Sheet l Filed Sept. 8,1958

LMNNSCSG Q INVENTOR Willard Co 0k, /W f ATTORN w. G. cooK TESION CONTROL SYSTEM -W. G, COOK TENSION CONTROL SYSTEM Filed Sepj.. 8, 1938 3 Sheets-Sheet 3 WITNESSES:

Patented Dec. 3, 1940 PATENT OFFICE TENSION CONTROL SYSTEM Willard G. Cook, Wilkinsburg, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation oI.'

Pennsylvania Applicationseptember s, 193s, serial No. 228,922

7 Claims.

My invention relates, generally, to tensioning devices and, more particularly, to systems for maintaining predetermined tensions on a strip of material as it passes between adjacent work 6 devices.

In the production of' sheet steel, it is customary to pass the steel in the form of a strip through a plurality of reducing rolls simultaneously and to subject the strip to front and l back tension as it passes through the reducing rolls.

A very successful system for providing strip tension in a strip rolling mill is disclosed in the copending application of G. P. Lessmann, Serial 'l5 No. 133,419, filed March 27, 1937, now Patent No. 2,189,609, issued February 6, 1940, and having a common assignee with the present application. This system comprises, generally, an idling roller which is caused to bear against the strip to deflect it from its normal pass line and thus subject the strip to tension. The operating system for the tensioning device is so arranged as to provide a predetermined range of strip tensions within aggiven range of strip deiiection, the deflection of the strip being kept lwithin a given range by automatic speed control of the reducing rolls by means of a vibrating regulator. vSuch strip ,tensioning systems that utilize a regulatorvof the vibrating type do `not have the speed of response, the wide range of regulation,

the simpilcity, and low of manufacture, installation and maintenan'c'ethat isA required in some rolling mills.

It isfan object of my invention, therefore, to provide an improved control system for a strip tensioning device.

Another object of my invention is to provideV a controlsystem for a strip tensioning device which shallifunction to provide rapid response to changes in speed and tension conditions and function to quickly correct any of these conditions within a wide range of degrees of required correction to thereby maintain, as vnear as possible, the desired tension conditions on the strip.

Another object of the invention is to provide a control system for a strip tensioning device which shall be simple and eilicient in construction and operation and inexpensive to' manufacture, install and maintain. l

'I'hese and other objects land advantages of my invention will be apparent from`.the following detailed description taken' in connection with the accompanying drawings, in which:

Figure 1 is a diagrammatic representation' of u' a portion of a strip rollingmill embodying the `reducing-rolls I4 and I6. The tensioning device I Il functions ito maintain a desired tension on the strip I2 within a predetermined range of 15 strip deection. I'he deection of the strip I2 by the tensioning device I0 is kept within the desired range by speed control of the drive motor I8 for the rolls of the roll stan'd I6. The speed of the drive motor I8 is controlled by con- 20 trolling the excitation of an exciter generator 20, which provides the excitation current for the motor I8. The excitation of the exciter generator 20 is controlled -by a regulator 22, which vis disposed to be actuated in accordance with 245 the variations inthe deflectionAof the strip I2 by the tensioning device I0.-

Referring to Fig. 1 for a detailed description of the preferred embodiment` of my invention, the tensioning device l0 comprises a bell crank 30 24 having arms 26 and 28 and pivotally mounted on the support 30. An idling roller 32 is rotatably mounted upon the arm 26 to bear against the strip I2 and to thus tension the strip by deflecting it from its normal pass line between the 35 roll stands I4 and I6. A piston 34 acts upon the bell crank arm 28 to force the tensioning roller 32 against the strip I2, under the influence of fluid pressure which is maintained at a substantiallynconstant amount by means of a 40 pressure regulating valve 36, which is connected between the pressure fluid reservoir and the piston 34. The pressure regulating valve 36' may be adjusted to provide any desired constant pressure acting upon the piston 34 by adjust- 45 ment of the energization of the solenoid 38 by Vmeans of the rheostat 48.

As is explained in detail in the above-referred to application Serial No. 133,419, the angular displacement of the bell crank arms 26 and 28 is 50 substantially 51, and when the lbell crank arm 28 is maintained substantially parallel to the normal pass line between the roll stands Hand I6 and a substantially constant force is applied to'theV bell crank arm 28'by the piston 34, the 55 strip I2 will be subjected to a substantially constant tension by the tensioning roller 32 within a limited range of strip deflections. The bell crank 24 is connected by means of 5 a shaft 42 to rotate a synchro-tie transmitter unit 44, which in turn is electrically connected to operate the synchro-tie receiver unit 46 in a well-known manner. The synchro-tie receiver unit 48 is mechanically connected to actuate the l cam 48 by means of a shaft 58.

A stack of elongated conducting strips 52 is provided, and these strips are insulated from each other by insulating members 54. Each of` the strips 52 is provided' with a contact element l 58 extending to each side Aoi the strip, each of the contact elements 58 being disposed opposite the contact element on the adjacent strip so that contact between each strip and its adjacent strip will be made when the strips are moved closely together. `The strips 52 are made of spring material and are so dimensioned and so disposed with respect to a stop block 58 as to permit their ends to engage the block 58 -and hold the strips in spaced relation with each other.

The cam 48 acts upon an arm 60, having a pivotal support 62,.against the bias of a spring 64. A pin 66 is mounted upon the arm 6I), as shown, so as to engage the uppermost strip 52 and move it into contact relation with the next strip and to thus move the successive strips into contact relation with their adjacent strips.

A resistance element 68 has several taps, as shown, each connected to one of the strips 52 so that as the strips are moved in contact rela- .'35 tion with each other the sections of the resistance element 68 connected with the strips which are in contact with each other will be short-circuited, thus decreasing the effective resistance of the resistance element 68. The resistance element 68 40 is connected in series circuit relation with the field winding 18 of the exciter generator 20, and an adjustable resistance 1I to a suitable source of direct current as shown. Thus the excitation of the exciter generator 20 and, therefore, its output potential will be varied by the regulator 22 in accordance with the degree of deflection of the strip I2 by the tensioning device III. The adjustable resistance 1I is provided to make any desired adjustment in the output potential of the exciter generator 20. The exciter-generator 2U is continuously driven at a substantially constant speed by any suitable motorl 12 and has its armature connected in series circuit relationthrough ,the adjustable resistance 14 with the field Winding 16 of the drive motor I8 for the roll stand I6. Thus the speed of the motor I8 may be adjusted by the adjustable resistance 14 and will also be varied in accordance with'variations in the output potential of the exciter generator 20.

In the operation of the device of Fig. 1, the

tensioning device will operate to maintain a substantially constant tension upon the strip I2, while the deflection of the strip is maintained between predetermined limits. If, for any reason,

the amount of slack in the strip I2 between the roll stands I4 and I6 should decrease, it will be seen that the bell crank 24 of the tensioning device Ill will be rotated in a counter-clockwise direction, and this 'movement will be transmitted through the synchro-tie sending and receiving units 44 and 48 to the cam 48, which will cause a downward movement of the pin 66. The downward movement of the pin 66 will cause a number of the strips 52 to be moved away from the block 58 and so that their contact elements 56 will be moved into engagement with each other. to yshort--circuit a number of the sections of the resistance element 68, the number depending upon the amount of the change of the deflection of the strip, to thus increase the excitation of 5 the exciter generator 20 and in turn increase its output potential. This increase in the output potential of the exciter generator 20 will increase the excitation of the motor I8 which will cause the motor to decrease its speed, thus permitting l0 an increase in the slack of the strip I2 between the roll stands I4 and I6 and, therefore, an increased deflection of the strip I2 by the tensioning device I0. In a similar manner, the speed of the motor I8 will be increased by an increase in.15 the deflection of the strip I2 by the tensioning device III to bring the deflection of the strip I2 back to within the desiredI predetermined limits. In the tensioning control system of Fig. 2, a stack of resistance plates 18 is provided, and each 20 of these plates is separated from the adjoining plate by a metallic contact plate 80. Each of the resistance plates 18 has mounted thereon near one end a contact element 82, the contact elementsV 82 being disposed to engage each other 25 successively as the stack of plates is rocked in a counter-clockwise direction with the stack of contact plates serving as a pivot point.y An arm 84 is connected to be rotated by the shaft 58, and has mounted thereon the pin members 86 and 3 88 which bear upon a metallic plate 98 which is mounted above the stack of resistance plates 18. Each of 'the resistance plates 18 has an insulating plate 9I mounted thereon which prevents electrical contact between the right-hand 3: ends of the plates 18. J

As the plate 90 is rocked in a counter-clockwise direction by the arm 84, it will be seen that the contact element 82 of the plate 90 and the uppermost resistance plate 18 will engage, and as the 4| stack is further rocked in the counter-clockwise direction, successive contact elements 82 will engage each other, thus providing a series of short circuits for the stack of resistance plates. As the resistance plates 18 are rocked, the contact re- 4 sistance between the plates 18 and the contact plates 80 is decreased. Thus, the rocking of the arm 84 in the counter-clockwise direction will both decrease the contact resistance between the seriesof contact plates 80 and the resistance 5 plates 18 and successively short out these contact resistances, so that the effective resistance of the stack of plates will be decreased as the arm 84 continues to rotate in the counter-clockwise direction.l The lowermost resistance plate is con- 5 nected to a suitable source of direct current, as shown, and the metallic plate 90 is connected in circuit with the field winding 10 of the generator 20 and a suitable adjustable resistance 1I to the other side of the source of direct current. e The operation of the tensioning control system shown in Fig. 2 is similar to that described in connection with the system shown in Fig. 1, the regulation of the speed of the drive motor I8 to maintain the degree of deflection of the strip I2 within the desired predetermined limits being controlled by the regulator 22, as hereinbefore described, in response to variations in the angular displacement of the tensioning device l0 with respect to the strip l2. 1 The tension regulating system of Fig. 3 is generally similar to those shown in Figs. l and 2, and includes an arm 92 pivotally mounted on a support 93 and biased against the cam 48, which is actuated by the synchro-tie receiver unit, by a I spring member 94. Ihe arm 92 is connected through a rod 99 to vary the compression force applied to a rheostat 99 of the carbon-pile type comprising a stack of `resistance plates I 90. In this device, the eiective resistance of the rheostat 99 will be varied by variations in the deilection of the strip I2 by the tensioning device I0 through the action of the cam 49 upon the arm 92. The rheostat 99 is connected in series circuit relation with the iield winding 'l0 of the exciter generator 20, and the variation of its efiective resistance Iwill thus vary the excitation of the exciter generator 29 to in turn vary the speed of the motor I9 by controlling its iield excita` tion.

Y In the operation of lthe system of Fig. 3, it

will be seen that the deilection of the strip willbe maintained within predetermined limits through the action of the regulator 22 upon the vexcitation of the drive motor I9 of the roll stand I9. f

In the discussion of the operation of these tension control systems, it has been assumed that the strip I2 is moving in the direction shown by the arrow adjacent the strip, and that the speed oi' the roll standhas been maintained constant, thus requiring that any changes in the amount oi.' slack in the strip I2 between the roll stands I4 and I6 be varied by means of speed variation oi' the drive motor I9 for the roll stand I9. It is to be understood that it is within the scope of this invention to control the speed of the drive motor for the roll stand I 4 in asimilar manner instead of the drive motor I9 of the roll stand I9, or that the drive motors for both roll stand I4 and roll stand I9 may be controlled by my tensioning, control device. ,l

It will be seen that I have provided a simple, emcient and inexpensive control system for maintaining predetermined adjustable tensions on a strip of material as'it passes between adjacent work devices which will iunction' to return the strip to the desired tension should any deviation from this tension occur, and which will quickly and efficiently function to return the strip to thedesired tension over a wide range of variations from this desired tension.

In compliance with the requirements of the patent statutes, I have shown and described herein the preferred embodiments of my invention. It is understood, however, that the Invention is not limited to the precise constructions shown herein, but is capable of modification by one skilled in the art, the embodiments herein shown being merely illustrative of theprinciples of my invention.

I claim as my invention:

1. In a system for subjecting a strip of material to tension as it passes between adjacent roll stands 'of a strip rolling mill, comprising a tensioning roller disposed to be madeto bear upon the strip to deilect it from its normal pass line between the roll stands and thus subject the strip to tension, means for actuating said roller to bear against the strip including means for automatically varying the transverse force applied to the strip vby the roller in accordance with its strip deecting operating position to subject the strip to a substantially consant tension, an

resistor, thereby to maintain the relative speeds of the sets of 'rolls of the roll stands such as to hold the tenioning roller Within predetermined operating limits.

2. In a system for subjecting a strip of material to tension as it passes between adjacent roll stands oi a strip rolling mill, comprising a tensioning roller disposed to be made to bear upon the strip to deflect it from its normal pass line between the roll stands and thus subject the strip to tension, means for actuating said roller to bear against the strip including means for automatically varying the transverse force applied to the strip by the roller in accordance with its strip deflecting operating position to subject thejstrip to a substantially constant tension, an electric drive motor for the rolls of one of the roll stands, a carbon-pile type rheostat connected to control the speed of said drive motor, and means for varying the effective resistance of said rheostat in accordance with the variations in the degree of deiiection of the strip by said roller, whereby, the deflection of the strip bythe roller is kept within predetermined limits.

3. In a system for subjecting a strip of material to tension as it passes between adjacent roll stands of a strip rolling mill, comprising a tensioning roller disposed to be made to bear upon the strip to deiiect it from its normal pass line between the roll stands and thus subject the strip to tension, means for actuating said roller to bear against the strip including means for automatically varying the transverse force applied to the strip' by the roller in accordance with its strip defiecting operating position to subject the strip to a substantially constant tension, anv electric drive motor for the rolls of one of the roll stands, a resistor connected in speed controlling relation with said drive motor, a plurality of flexible members arranged with corresponding ends clamped in xed relation and connected to separate points along said resistor, said xed ends being insulated from one another, the other ends of said flexible members being free to move, a movement limiting stop against which the free ends of said ilexible members are biased for positioning them in spaced relation, and` means controlled in accordance with the degree of deection of the strip for actuating said iiexible members from engagement with said stop and into circuit closing engagement with adjacent members to shortcircuit selected portions of said resistor to thereby limit the degree of deflection of the strip by said tensioning roller. l

4. In a system for subjecting a. strip of material to tension as it passes between adjacent roll stands of a strip rolling mill, comprising a tensioning roller disposed to be made to bear upon the strip to deflect itffrom its normal pass line between the roll stands and thus subject the strip to tension, means for actuating said roller to bear against the strip including means for automatically varying the transverse force applied to the strip by the roller in accordance with its strip deectlng operating position to subject the strip to a. substantially constant tension, an electric drive motor for the rolls of one of the roll stands, a stack of resistance plates, a metal contact plate disposed between each resistance plate and the adjacent resistance plate, said contact plates being narrower than said Y resistance plates and being disposed in alignvment soas to. provide a rocking pivot for said stack of resistance plates, each of said resistance plates having an end extending beyond its associated contact plates, the ends being normally spaced from each other by the contact plates between the resistance plates, a contact ele- 5 ment mounted on each of said. resistance plates spaced toward the ends of the plates from the contact plates, said contact elements being normally separated from eachA other and disposed to cause engagement of said contact elements each with the succeeding one as the stack of resistance plates is displaced about the pivot formed by the series of contact plates, such displacement causing variation of the contact resistance between the contact plates and the resistance plates, means whereby the speed of said drive motor is controlled by the effective resistance of the stack of contact plates and resistance plates, and means for varying the displacement of said stack of plates in accordance with the variations in the degree of deflection of ythe strip by said roller, whereby the deflection of the strip by the roller is kept within predetermined limits.

5. In a system for subjectingA a strip of material to tension as it passes between adjacent roll stands of a strip rolling mill, comprising a tensioning roller disposed to be made to bear upon the strip to deiiect it from its normal pass line between the roll stands and thus subject the n strip to tension, means for actuating said roller to bear against the strip including means for automatically varying the transverse force applied to the strip by the roller in accordance with its strip deecting operating position to subject the strip to a substantially constant tension, an electric drive motor for the rolls of one of the roll stands, a variable voltage generator for exciting said drive motor, a carbon-pile type rheostat connected toI control the excitation of said generator, and means for varying the effective resistance of said rheostat in accordance with variations in the degree of deflection of the strip by said roller, whereby the deflection of the strip by the roller'is kept within predetermined limits.

6. In a system for subjecting a strip of material to tension as it passes between adjacent roll stands of a strip rolling mill, comprising atensloning rollerv disposedto be made to bear upon o the strip to deilect it from its normal pass line between the roll stands and thus subject the strip to tension, means for actuating said roller to bear against the strip including means for automatically varying the transverse' force applied tothe strip by the roller in accordance with its strip deecting operating position to subject the strip to asubstantially constant tension, an

. electric drive motor for the rolls of one of the roll stands, a variable voltage generator for exciting said drive motor, a resistor connected in excitation controlling relation with said generator, a plurality of flexible members arranged with corresponding ends clamped in xed relation and connected to separate points along said resistor, said fixed ends being insulated from one another, the other ends of said flexible members being i'ree to move, a movement limiting stop against which the free ends of said ilexible members are biased for positioning them in spaced relation, and means controlled in accordance with the degree of deflection of the strip for ractuating said flexible members from engagement with said stop and into circuit closing engagement with adjacent members to short-circuit selected portions of said resistor to thereby limit the degree of deflection of the strip by said tensioning roller.

7. In a system for subjecting a strip of material to tension as it passes between adjacent roll stands of a strip rolling mill, comprising a tensioning roller disposed to be made to bear upon the strip to deflect it from its normal pass line between the roll stands and thus subject the strip to tension, means for actuating said roller to bear against the strip including means for automatically varying the transverse force applied to the strip by the roller in accordance with its strip defiecting operating position to subject the strip to a substantially constant tensionLan electric drive motor for the rolls of one of the roll stands, a variable voltage generator for exciting said drive motor, a stack of resistance plates, a metal contact plate disposed between each resistance plate and the adjacent resistance plate, said contact plates being narrower than said resistance plates and being disposed in alignment so as to provide a rocking pivot forvsaid stack of resistance plates, each of said resistance plates having an end extending beyond its associated contact plates, the ends being normally spaced from each other by the contact plates between the resistance plates, a contact element mounted on each of said resistance plates spaced toward the ends of the plates from the contact plates, said contact elements being normally separated from each other and disposed to cause engagement of said contact elements each with a succeeding one as the stack oi resistance plates isdisplaced about the pivot formed by the series of contact plates,

VYsuch displacement causing variation of the contat resistance between the contact plates and the resistance plates, means whereby the excitation of said generator is controlled by the eiective resistance of the stack of contact plates and resistance plates, and means yfor varying the displacement of said stack of plates in accordance with the variations in the degree of defiection of the strip by said roller, whereby the deflection of the strip by the roller is kept within predetermined limits.

WILLARD G. COOK.

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